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authorAlexei Starovoitov <ast@kernel.org>2015-11-29 16:59:35 -0800
committerDavid S. Miller <davem@davemloft.net>2015-12-02 23:36:00 -0500
commit01b3f52157ff5a47d6d8d796f396a4b34a53c61d (patch)
treec20181b1b6da1127b53b329085562a9ea2993ca4 /kernel/bpf
parenta64f3f83505f4ed6662fd9dda998d4890aba58bd (diff)
downloadlinux-sh-01b3f52157ff5a47d6d8d796f396a4b34a53c61d.tar.gz
bpf: fix allocation warnings in bpf maps and integer overflow
For large map->value_size the user space can trigger memory allocation warnings like: WARNING: CPU: 2 PID: 11122 at mm/page_alloc.c:2989 __alloc_pages_nodemask+0x695/0x14e0() Call Trace: [< inline >] __dump_stack lib/dump_stack.c:15 [<ffffffff82743b56>] dump_stack+0x68/0x92 lib/dump_stack.c:50 [<ffffffff81244ec9>] warn_slowpath_common+0xd9/0x140 kernel/panic.c:460 [<ffffffff812450f9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:493 [< inline >] __alloc_pages_slowpath mm/page_alloc.c:2989 [<ffffffff81554e95>] __alloc_pages_nodemask+0x695/0x14e0 mm/page_alloc.c:3235 [<ffffffff816188fe>] alloc_pages_current+0xee/0x340 mm/mempolicy.c:2055 [< inline >] alloc_pages include/linux/gfp.h:451 [<ffffffff81550706>] alloc_kmem_pages+0x16/0xf0 mm/page_alloc.c:3414 [<ffffffff815a1c89>] kmalloc_order+0x19/0x60 mm/slab_common.c:1007 [<ffffffff815a1cef>] kmalloc_order_trace+0x1f/0xa0 mm/slab_common.c:1018 [< inline >] kmalloc_large include/linux/slab.h:390 [<ffffffff81627784>] __kmalloc+0x234/0x250 mm/slub.c:3525 [< inline >] kmalloc include/linux/slab.h:463 [< inline >] map_update_elem kernel/bpf/syscall.c:288 [< inline >] SYSC_bpf kernel/bpf/syscall.c:744 To avoid never succeeding kmalloc with order >= MAX_ORDER check that elem->value_size and computed elem_size are within limits for both hash and array type maps. Also add __GFP_NOWARN to kmalloc(value_size | elem_size) to avoid OOM warnings. Note kmalloc(key_size) is highly unlikely to trigger OOM, since key_size <= 512, so keep those kmalloc-s as-is. Large value_size can cause integer overflows in elem_size and map.pages formulas, so check for that as well. Fixes: aaac3ba95e4c ("bpf: charge user for creation of BPF maps and programs") Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/arraymap.c8
-rw-r--r--kernel/bpf/hashtab.c34
-rw-r--r--kernel/bpf/syscall.c4
3 files changed, 34 insertions, 12 deletions
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 4c67ce39732e..b0799bced518 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -28,11 +28,17 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
attr->value_size == 0)
return ERR_PTR(-EINVAL);
+ if (attr->value_size >= 1 << (KMALLOC_SHIFT_MAX - 1))
+ /* if value_size is bigger, the user space won't be able to
+ * access the elements.
+ */
+ return ERR_PTR(-E2BIG);
+
elem_size = round_up(attr->value_size, 8);
/* check round_up into zero and u32 overflow */
if (elem_size == 0 ||
- attr->max_entries > (U32_MAX - sizeof(*array)) / elem_size)
+ attr->max_entries > (U32_MAX - PAGE_SIZE - sizeof(*array)) / elem_size)
return ERR_PTR(-ENOMEM);
array_size = sizeof(*array) + attr->max_entries * elem_size;
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 19909b22b4f8..34777b3746fa 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -64,12 +64,35 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
*/
goto free_htab;
- err = -ENOMEM;
+ if (htab->map.value_size >= (1 << (KMALLOC_SHIFT_MAX - 1)) -
+ MAX_BPF_STACK - sizeof(struct htab_elem))
+ /* if value_size is bigger, the user space won't be able to
+ * access the elements via bpf syscall. This check also makes
+ * sure that the elem_size doesn't overflow and it's
+ * kmalloc-able later in htab_map_update_elem()
+ */
+ goto free_htab;
+
+ htab->elem_size = sizeof(struct htab_elem) +
+ round_up(htab->map.key_size, 8) +
+ htab->map.value_size;
+
/* prevent zero size kmalloc and check for u32 overflow */
if (htab->n_buckets == 0 ||
htab->n_buckets > U32_MAX / sizeof(struct hlist_head))
goto free_htab;
+ if ((u64) htab->n_buckets * sizeof(struct hlist_head) +
+ (u64) htab->elem_size * htab->map.max_entries >=
+ U32_MAX - PAGE_SIZE)
+ /* make sure page count doesn't overflow */
+ goto free_htab;
+
+ htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
+ htab->elem_size * htab->map.max_entries,
+ PAGE_SIZE) >> PAGE_SHIFT;
+
+ err = -ENOMEM;
htab->buckets = kmalloc_array(htab->n_buckets, sizeof(struct hlist_head),
GFP_USER | __GFP_NOWARN);
@@ -85,13 +108,6 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
raw_spin_lock_init(&htab->lock);
htab->count = 0;
- htab->elem_size = sizeof(struct htab_elem) +
- round_up(htab->map.key_size, 8) +
- htab->map.value_size;
-
- htab->map.pages = round_up(htab->n_buckets * sizeof(struct hlist_head) +
- htab->elem_size * htab->map.max_entries,
- PAGE_SIZE) >> PAGE_SHIFT;
return &htab->map;
free_htab:
@@ -222,7 +238,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
WARN_ON_ONCE(!rcu_read_lock_held());
/* allocate new element outside of lock */
- l_new = kmalloc(htab->elem_size, GFP_ATOMIC);
+ l_new = kmalloc(htab->elem_size, GFP_ATOMIC | __GFP_NOWARN);
if (!l_new)
return -ENOMEM;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4a8f3c1d7da6..3b39550d8485 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -240,7 +240,7 @@ static int map_lookup_elem(union bpf_attr *attr)
goto free_key;
err = -ENOMEM;
- value = kmalloc(map->value_size, GFP_USER);
+ value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
if (!value)
goto free_key;
@@ -299,7 +299,7 @@ static int map_update_elem(union bpf_attr *attr)
goto free_key;
err = -ENOMEM;
- value = kmalloc(map->value_size, GFP_USER);
+ value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
if (!value)
goto free_key;